


As Beautiful as the Sea, Glistening so Dangerously

by M00n_Slippers



Category: Batman (Comics), Batman - All Media Types, Red Hood and the Outlaws (Comics), Red Robin (Comics), Robin (Comics), Under the Red Hood
Genre: Alternate Universe - Merpeople, Dubious Consent, Historical AU, Interspecies Sex, Jason being scary but sexy, Knotting, M/M, Mer AU, Mer Jason, Mer/Human sex, Mermen, Other, Size Kink, Sort Of, The alternate title for this fic is 'The Mer Banger', Tim being a little creepy and also stupid, Xenophilia, big dick problems, fuck and run, intersex Mer, monster sex?, the time period is vague, this is just weird smut, tripod Tim, urethal play
Language: English
Status: Completed
Published: 2019-09-21
Updated: 2019-09-21
Packaged: 2020-10-25 05:04:39
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,193
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20718557
Author URL: https://archiveofourown.org/users/M00n_Slippers/pseuds/M00n_Slippers
Summary: Consummating his sexual attraction to a wild Mer can only end in being mauled, but apparently Tim is just that horny.





	As Beautiful as the Sea, Glistening so Dangerously

**Author's Note:**

> Not going to lie, I'm weirdly embarrassed that I wrote smut this weird even though I love it when other writers write me smut this weird, but what the hell. Hope you guys enjoy it. I have some ideas for additional chapters so I might add on to this at some point.
> 
> I'm shit at titles so I did the song lyric title thing. The line is from "Only Human" by Misterwives.

The idea was crazy. It was dangerous and probably more than a little disgusting, but Tim couldn't get it out of his head. Ever since he'd seen the mer laying on the sandy beach in the sheltered cove near Wayne manor, it's devastatingly attractive human half on full display above the water line, glistening tail reaching into the sea and slapping at the waves to signal it was ready to mate—well, it was all Tim could think about.

Mers had been known to kill humans when they got too close. There were legends and rumors of people bedding them, of sirens seducing men and women, but he'd never heard of it happening for real. So this fantasy that kept playing in Tim's mind, that he'd just walk up to this mer one day and fuck it, just sink his dick into the mer's deep slit, was more likely to end in Tim's brutal death than anything else. It needed to stop. The fact that he kept thinking about it, fantasizing and planning and checking the cove for a glimpse of the creature was insane. It was all because of what was going on at home, he told himself. This was just a phase. At least, if he treated it that way, maybe it would go away like one?

But this was an ongoing problem with no solution in sight. “No, this isn’t going to work,” one young man said with wide, scared eyes, as soon as Tim dropped his trousers. “I can't do it, it just hurts,” a female partner told him after he'd been trying to push into her for five minutes even with extensive foreplay. Over and over it went. He couldn't satisfy anyone, and he could never be satisfied by them.

Tim kept his dalliances private, those few he had. Much more private than the majority of youth his age and in his social scene who went roving the towns for brothels or amenable bar maids or stable boys to use as proof of their sexual prowess. Tim had never felt the need to do such things. Not only did he respect his partners too much to use them like that, but he really didn't want to draw any attention to his own sexual ability, which was demonstrably terrible.

The problem was Tim was just too big. It sounded like a great problem to have but it really wasn't. Tim's clothes had to be specially tailored to hide his size even when he was flaccid. When he did get aroused not only was it obscenely obvious, but he felt light-headed from the amount of blood rushing between his legs. Anyone he tried to enter inevitably said it hurt, even after the most careful and loving preparations, and even when they suffered through it for him he couldn't fit, he reached the end of their depth long before he could completely settle inside. He'd never had a satisfying sexual experience in his life, and after his last partner had gossiped about their failed coupling, now everyone else in Gotham knew it as well.

It was...humiliating. Some days Tim could barely stand to show his face in public, so he escaped in any way he could justify, with horseback rides and walks and independent study and training in the sword or staff. Since the weather had been good, he'd taken to walking the beach near the cliffs along the extreme edges of the manor grounds. Despite the spot's natural beauty, there was a difficult climb along sharp and steep rocks to get to the cove below with its banks of fine sand.

The first few times he'd been there, Tim just sat on a rock and tossed the occasional pebble or shell into the water as he listened to the waves go in and out. It was calming, isolated. No one could see his loneliness as the waves roared in his ears, crashing on rocks and rushing toward the sand, drowning out his negative thoughts.

But then one day he'd seen the mer there.

He'd mostly only seen glimpses of mer from the docks, so brief they might have been sharks or dolphins or seals, or just a strange slap of waves. He'd seen others dead, washed onto shore or caught in nets, bloated with decay. They never looked so human then, and he'd never seen one so huge. This mer—his mer—was dark-haired, broad and muscular of the type that looked like a male, and a tail that was nearly twice Tim's height in length. No Mers were actually male or female, as Tim had been taught by a tutor while examining a recently dead corpse on the dock. They were both, with a cock that rivaled Tim's own that retracted neatly within their slit and left room for the mate's to push into and inseminate.

After discovering his mer on the cove, Tim had done more research of his own. Mers were large and dangerous creatures, but the occasional whale, dolphin, shark or great squid had been known to take advantage of their vulnerability when mating. Other Mers would also attack to steal mates, or so the books said, so mers would mate on land, where they had few predators, and where they could easily turn and escape if one came along.

Tim's mer had clearly come onto land to mate, basking on the sand and slapping its heavy red and black tail in the water as the waves rushed up the beach, over and over, day after day. Occasionally it would shift its body, whipping its long tail in sinuous lines that dragged against the sand. It would arch its human body, stretching stiffly, sometimes its long, thick cock would peak from its slit, engorged and needy, before retracting back inside for protection.

That was what really got Tim thinking these ridiculous thoughts. Maybe none of his human partners could satisfy Tim, but he should fit into a mer just fine. He wanted it so bad he'd pleasure himself at night thinking about it, gripping himself with both hands, fingers fighting to close around his base, trying to imagine the feeling of every part of him being completely, tightly encircled. He'd thrust until he was out of breath and spilling into his lap.

Tim didn't explicitly tell himself he was going to do it, but the flutter of his heart, the way it pounded in his ears as he walked the trail to his and the mer's secret cove, was different than other days. Would the mer be there? It had been every day for nearly a week. But how long did mer mating season last? Did they even have season? Maybe he was gone? Tim didn't know but his loins felt eager and his clothes from the anticipation in his gut already causing his dick to fill.

As he scrambled down the rocks, Tim just kept imagining it, even as images of sailors and fisherman who had tangled with mer and come away from the encounter with scared slashes and missing eyes and fingers came to mind. He was an idiot. A horny idiot. But he wasn't stopping. His crotch was bulging with his arousal in a way that would have mortified him in decent company and opened him up to ridicule and he still wasn't stopping.

He heard the mer before he saw it, it's tail slapping the water. This was about when Tim would pause at a shelf in the rocks and simply watch, but he kept climbing down until he reached sand, hot against his feet from the sun baking down on it, and turned around with his pulse thumping fast and hard in his throat.

The mer was there, waiting. This close he could see how muscular it was, no doubt from life fighting against the weight of water and dragging it's huge, heavy body along the shore. Tim swallowed, eying it's swollen biceps and pectorals, and the chiseled definition of it's abs with desire. The fact that it's physical perfection was marred with scars from octopus suckers and fishing spears and jellyfish stings somehow made it's body that much more interesting. It's face was attractive and deceptively human, with it's handsome lines, straight nose and fine black waves of short hair. When it saw Tim appear, the mer's body went rigid and lay perfectly still and silent, it's silvery eyes starring at him, watching Tim's movement with caution and something that on a human he would call curiosity.

Tim wasn't certain how smart mer were. Some people insisted they were as dumb as fish, but others said they were as clever as a human. That they could imitate human words and dolphin calls alike, even speak to each other in their own languages. Tim didn't know, he'd never been this close to one before.

“I've been w-watching you,” Tim said to the mer, his words quivering with nerves as he took a step toward the creature where it lay near the water, the waves rushing high enough to keep it's fish-half damp. No response, the mer didn't move, just lay there looking like something from a beatific nightmare, or maybe a terrifying fantasy.

“You're waiting for a mate,” Tim said, swallowing with nerves and marveling at his own audacity. “I-I could be your mate.”

The mer continued to stare at him, unreadable. It looked him up and down, eyes slightly narrowed. Was that skepticism? Wariness? Or was Tim just reading human emotions into the expressions of something that wasn't capable of them?

Tim slowly lifted his hand and the mer's mouth twisted into a hiss like a crocodile and deep in it's throat began an ominous clicking. Tim palmed the erection trapped within his pants, watching the mer's scaled lower body coil and flick it's tail in agitation, making deep grooves in the dark, damp sand of the shoreline. Tim was captivated by it's slit, by the way the head of the creature's cock would occasionally push out of the folds and disappear back within. He undid the buttons of his pants and slipped himself out of his underwear, smelling the brine of the water, listening to the creature's clicking, sighing in relief as the tightness trapping him finally eased.

Looking down at himself Tim reeled at the image he saw, at once ashamed and fascinated by his own size. Tim's cock was thicker than his wrist and blood red, twitching against it's own weight as it unsheathed and swelled to hardness. Tim felt light-headed, the edge of his vision grainy. Something about the nervous anticipation and his extreme arousal was leaving his pulse thready even as it left him stiffer than he'd ever been in his life. Aching to be touched, Tim took himself in hand, hot and sensitive, and stroked from base to tip, pulling his cock straight up along his body, reaching past his navel with its great length.

Abruptly the clicking from the mer stopped and it made an interested trill and laid back into the sand. Tim was enraptured by it's silvery eyes that seemed to call him and against all better judgment, Tim slipped out of his pants and underwear completely, letting them fall to the sand and stepped tentatively forward until the cold, dark water splashed his ankles.

Walking like this was not comfortable, the meaty slap of his balls against his thighs, large and proportional to his overly massive cock, was a sound that made Tim burn with embarrassment. The strain of his engorged penis, twitching as it fought to rise up against it's own weight, made him feel like he needed to lay down and get some blood into his brain. But as Tim walked forward all he could think about was sinking into this mer.

The mer lay suspiciously placid, grains of salt and sand clinging to the curves of it's scarred skin, it's powerful tail still and unmoving as Tim approached and breached what he perceived as the boundary of safety. They were close enough to reach out and touch. The mer could savage Tim at any second if it desired, could rend him with it's clawed fingers, or bash him with it's powerful tail or rip out his throat with it's shark-like teeth. This was permission, right? Somehow, this was happening just like he'd dreamed.

Tim stepped over the fish-half of the mer, foot landing on uneven wet sand, his legs forced to splay wider than he expected to accommodate the width of the mer's body. He nearly stumbled onto his knees, trying to position himself above the mer, behind it's slit. The tail of this mer was thick and muscular, changing from pale, flesh colored scales where it met the torso, to bright crimson and then black near the fin. Looking down at the mer behind the firmness of his own jutting cock, it stared up at him with an expression Tim could only call 'seductive'. As if in a trance, Tim sat down on the warm scales, their edges lightly scraping the skin of his ass and reached out with shaking fingers to the mer's slit, just below the start of it's scales while the mer watched his movements with a strange intensity.

The creature's slit was wet and warm and smooth to the touch, slick in a sticky way that didn't wash off in the sea water. Tim teased at the opening, watching the mer's expression ease into something that might be contentment as Tim slipped a finger inside and explored along the edges. At the top of the slit he felt the creature's cock, the head bulbous and blunt with ridges that might help it stay inside a mate. Tim felt along blindly, discovering it's shape until the mer made a sound like a sigh and the cockhead pushed out of the slit and started to rise to it's impressive, fully unsheathed length. Compared to Tim's own size, the mer's was still bigger. Thick enough to need both Tim's hands to fully wrap around it's diameter, and a dusky pink like the inside of a shell. Tim groped at it with interest, exploring every vein and wrinkle, running his thumb over the creature's urethra until he could feel the opening start to give around his finger as he teased at it.

“You're big, huh?” Tim heard himself say with awe. “Like me.” Was this how others felt when they saw Tim's sex? Did they think it huge and monstrous? Tim just wanted to get his mouth on it but he had the vague feeling it might seem threatening and he probably shouldn't. But Tim wondered what it tasted like. It smelled like salt and fish and musk.

He stroked the creature's length, watched it squirm beneath him like a restless snake, felt the power in it's tail that could crush his skull with one well-aimed smack. It sent a thrill through Tim to know he was on top of something this beautiful and dangerous, something that could kill him in a dozen different ways, with teeth, or tail or talon or good old-fashion drowning.

Tim was fascinated with the large head of the creature's cock, with how the cap was so ridged and wide. He pressed his finger against the hole at the top that was leaking pearly liquid and kept pressing. The mer made a sound that was almost human, like a bitten off gasp, as Tim's first finger entered the creature's cockhead until he was inside down to the bed of his nail. The mer fidgeted beneath him, it's huge cock twitching like something alive as Tim relentlessly pushed passed the tightness and deeper into the creature, passed the knuckle. Tim gripped the base of it's member tight to keep it from bobbing or retracting as he pressed until his finger was completely inside.

“You're cock's so big I can use it like a hole to fuck in,” Tim said as he began to work his finger in and out, the way lubricated by dribbles of cum seeping from the tip. He worked the opening first slowly and then faster and faster until he was finger-fucking into the mer's cock at a blistering pace.

Now the mer was making sounds, deep animalistic moans that seemed almost out of Tim's range of hearing overlayed with much more human, heart-fluttering whimpers. Tim himself was making breathless sounds of need and humping against the creature's scaled body, his own tip dragging against the mer's even larger cock deliciously. Tim pulled his finger from the slit of the mer's dick and inserted his thickest, longest finger, quickly and harshly working it to it's base.

“You're so beautiful,” Tim heard himself say as he watched the creature's expression turn desperate, it's face lined with salty tear-stains, it's tail almost unseating Tim as it thrashed wildly beneath him.

“You've been waiting for me here all week, right? You knew I wanted you. And now you're letting me have you.”

Tim's eyes widened as he felt the base of the mer's cock start to expand like a balloon in his grip, spreading his fingers apart as the creature made a sound like a choked-off wail. Tim pulled his finger from the creature's cockhead and hastily pumped the mer's member in both hands, from cap to the inflated knot at it's base. Tim was nearly toppled right off of the mer's tail with a violent thrust of its hips as the creature released, spewing opaque semen like a fountain in quantities no human could. Tim kept pumping and squeezing his hands and the cock kept spurting in small bursts, splashing Tim's shirt and dripping down his fingers until he grew too tired to continue, the muscles in Tim's arms and wrists burning.

The creature's cock remained stiff and firm, but it's release allowed it's knot to shrink and it's penis to retract back inside the mer's slit. Beneath Tim, the mer's chest was heaving with it's mouth open, lined with sharp, pointed teeth. It's eyes fluttered open and shut, a pale membrane slanting over it's eyes and back as it blinked up at Tim, looking like all of his monstrous fantasies come to life. Beautiful. Tim was already tired from getting the creature off, his arms like jelly from pumping it's huge shaft, but his anticipation for the main event allowed him to set his weariness aside. He needed this.

Tim played with the pool of cum that had settled in the slope of the creature's waist, tracing the edges of abs and scales and the faint flecks and stripes patterning the transition from human to fish. He pushed his fingers into the mer's slit and scissored them, feeling it's hole tighten around him as he pushed under the sheathed cock and explored the deep, velvety channel, already imagining himself inside. He wanted it. Wanted it so bad his dick was twitching and weeping, fat with need.

Taking himself in hand, Tim moaned at the touch, his cock so hard and hot, pounding with blood. He was so aroused his dick had risen to jutt away from his body, which wasn't normal for him. It was usually too heavy to rise very much even at his stiffest, but right now he was so rock hard and erect it bordered on painful.

“You ready for me? I bet you are,” Tim said and lined himself up with the lips of the mer's opening, rubbing his cockhead over the folds, coating himself in the mer's slick. He could feel the warm heat and slippery edges of the mer's opening as it rubbed against his sensitive tip. When he finally breached the entrance, Tim cried out and snapped his hips forward, feeling himself push through the tight opening.

Tim gasped as he slipped inside, loose enough to move but snug enough to feel exquisite. “You feel so good,” he breathed, fighting not to come before he could fully experience the moment. “I bet you can take all of me, huh? I bet you want it as bad as I do.”

Tim drove his hips into the mer carelessly, forcing the channel to split around him, marveling at how it sucked him in, how it accommodated even Tim's intimidating girth. He teared up and whimpered in the extreme pleasure as his hips drove his cock deeper and deeper in, past where any partner had been able to accept his length and thickness before until the heat of the monster fully enveloped him from tip to root.

“Oh fuck,” he cried as his hips began to thrust against his control. Fuck, it felt amazing. It was everything he'd dreamt it would be and more. The tightness, the restriction, the friction against every veined inch of his dick as he dragged the shaft along the mer's walls. His balls bounced and swung as he slammed in and pulled out of the mer's opening, the sounds from his mouth growing louder and more wanton as he slid deep into the creature's cunt.

The mer began to make it's own desperate sounds again and Tim fucked in and out of him, artlessly, desperately. At some point he'd fallen almost completely onto the mer's chest, and in the moments when he could force his eyes to focus on anything around him he stared at it's plump chest and the rigid scar cutting across it and made weak attempts to mouth hungrily at the skin, enjoying the smoothness against his tongue.

Tim was building to a peak, chasing it with every muscle in his body, driving his hips into the mer's hole until his balls tightened against him. He fought to stay on that edge of ecstasy as long as he could, drawing out his enjoyment to it's utmost before Tim finally came, long and hard, pumping lines of hot cum into the mer's shaft. Bursts of color danced against his vision and he fought to drag air into his lungs.

Tim surfaced from the pleasure some time later blinking on top of the mer, having lost a few moments of consciousness. He lay against the mer's chest, feeling drowsy and content. With his eyes closed like this, he could almost forget about the fishy scales between his legs, the smell of brine and the webbing between the fingers, resting on his back. He could imagine he was with a human lover that could give him human love. Tim wanted to always be like this.

And then the wind was knocked from his body as inhuman strength shoved Tim into the sand. The mer rolled on top of him with blazing speed, digging its claws painfully into Tim's arm and pinning him beneath the weight of its massive body.

Fear shot through Tim. He panted with terror as the Mer considered him with frightening intelligence, so close he could smell the creature's breath. The mer could slit his jugular, could crush him with it's bare hands. It was a wild animal...a wild being? He was completely at it's mercy and Tim was an idiot. A stupid, horny, suicidal idiot.

He told himself that at least he got laid before he died, but it was a terrible consolation because all he wanted now was to do it again, as soon as possible. It hadn't been enough, he wanted more.

When the Mer spoke, Tim almost fainted with surprise.

“You wanna be my mate, huh? What a joke,” it smirked with wry, skillful syllables, revealing itself to be every bit as aware as Tim.

In that moment, everything Tim said rushed through his mind again and painted the picture of a complete moron. His face blushed red with embarrassment. God, what the hell had he been thinking? Tim had been fetishizing the Mer as some kind of prop he could just use, and here it was judging him. He just wanted to die, just let the mer kill him, he deserved it.

“But...I guess you'll do.”

Tim flinched as the mer dipped to sensuously lick over his neck and close it's lips in something like a sloppy kiss. All the while Tim lay perfectly still, trying to process what was happening to him, trying to decide what was going to keep him alive and if he wanted to bother.

When the mer pulled away and slapped sand in his face in it's hurry to get into the water and disappear back into the ocean, Tim felt the first throb of pain and realized he had a perfect bite mark at the juncture of his neck and shoulder. The mer's teeth had been so sharp he hadn't felt it until the blood started flowing.

He stared at the enigmatic ocean a while trying to figure out what had happened until the tide came up high enough to splash his balls and chase him further up the shore. Tim's legs felt shaky, his nerves shot from the mix of pleasure and terror he'd experienced. As Tim dusted sand from his crack and pulled his clothes back on, only one thing was on his mind.

How soon could he see the mer again?


End file.
